Color television reproducing system



Aug. 25, -1953 Filed Dec. 22, 1949 f Snuentor [Z212] M We Gtforneg Aug. 25, 1953 P. K. wElMER' 2,650,264

COLOR TELEVISION REPRODUCING SYSTEM Filed-Dec. 22, 1949 s, sheets-sheet 2` nventor 6% K. www

Aug. 25, 1953 P. K. wElMER 2,650,264

COLOR TELEVISION REPRODUCING SYSTEM Filed Dec. 22, 1949 3 Sheets-Sheet 3 Kfm/VER 4050 6477449 W05@ f y. I4

Ottorneg Patented Aug. 25, 1953 2,650,264 COLOR TELEVISION REPRODUCIN G SYSTEM Paul K. Weimer, Princeton,

N. J., assignor` to Radio Corporation of America, a corporation of Delaware Application December 22, 1949, Serial No. 134,453 32 clafnls. (o1. ris- 5.4)

This invention relates to signal display systems employing a single cathode ray tube for the display of signals in a plurality of different colors and particularly, but not necessarilyexclusively, to color television systems of this character wherein the reproducing tube is adapted to reproduce an image substantially in its natural colors.

Most of the television systems which have previously been devised for the reproduction of images substantially in their natural colors have been somewhat complex in nature. The complexity of a typical one of those prior art systems, which has had at least some practical success, is the result of the employment therein of a single reproducing tube in combination with a mechanically movable color filter device.

Among the disadvantages of the type of color television system embodying a prior art filter device are the additional space necessary to house the color filters, thereby increasing the size of the instrument, and the mechanical movement of the filter device, thereby producing objectionable noise and vibration. l

Furthermore, mechanically movable lter devices are obviously unsatisfactory for the dot multiplex type of color television system as such rapid change in color requires electronic devices for color selection and control.

In order to obviate disadvantages of the character described, it also has been proposed to effect the reproduction of the several color components of the image by means of a plurality of cathode ray image reproducing devices popularly known as the kinescope. While such systems have met with suicient success to Warrant their use in commercially practical `television receivers, they require an individual image reproducing device for each of the color components of the image to be reproduced. l

Accordingly, the principal object of the present invention is to provide an improved color telel vision reproducing system employing a single cathode ray tube for the reproduction of the primary color components of an image.

Another object of the invention' is to provide an improved form of cathode ray tube -by means of which a plurality of different color components of an image may be reproduced.

Still another object of the invention is to provide an improved color television image reproducing system embodying a single cathode ray tube having a novel electrode structure by means of which to selectively `control the movement of an electron beam over a `luminescent screen of` such a character that differently colored light is emitted from different areas thereof when excited by the electron beam.

A further objectof the invention is to provide an improved color television image reproducing system in which is embodied a cathode ray tube having a novel color-selecting electrode whereby, in addition to the conventional deflection of the beam over a fluorescent screen, the beam is selectively deflected to impinge upon sub-elemental areas of the screen capable respectively of emitting diferently colored light.

According to this invention, a television image is reproduced substantially in its natural colors by the use of a single cathode ray tube by deiiecting an electron beam in a predetermined pattern over a luminescent screen having individual areas thereof capable of emitting light of `different colors. The intensity of the beam is modulated in accordance with video signals representative of `a plurality of color components of the image to be reproduced. The velocity of the scanning beam is selectively varied to effect an `additional color-selecting deflection thereof, whereby to eX- cite the individual screen areas.

rIhe improved color television image reproducing system comprises a cathode ray tube provided with a luminescent screen having a plurality of groups of areas which are capable respectively of emitting differently colored light. The tube also is provided with a novel electron beam-controlling electrode by means of which to effect the controlled impingement of the electron beam upon selected ones of the screen areas. The system also includes means for receiving composite television signals and for employing the video signal component to modulate the intensity of the electron scanning beam. `There is further provided means operative concurrently with the color changes of the video signals for varying the velocity of the electron beam so that it is deiiected onto a particular screen area capable of emitting light of the color represented by `the video signal` by which the intensity of the beam is` modulated at that instant.

In accordance with one feature of the invention, the cathode ray image reproducing tube is provided with an apertured electrode located in the path` of the electron beam and having a conflgurationlsuch that energization thereof prol duces a plurality of electric fields transversely of the path of theV beam. As a result, the electron beam,` in Vtraversing any of the fields produced in the vicinity ofthe electrode apertures, isvari- `ably deflected depending upon the velocityof the image color components.

beam. Further, in accordance with the invention, the potential of the apertured electrode relative to the source of the electron beam is varied so as to produce the velocity variation of the beam.

In accordance with another particular feature of the invention, the apertured electrode by means of which the electron beam velocity is varied has a configuration such that the apertures thereof are of an asymmetric character. By suitably impressing potentials of predetermined magnitudes upon the apertured electrode and the luminescent screen, there is produced a i'leld therebetween which, in the vicinity of the electrode apertures, is distorted in such a manner as to produce a transverse component. The field distortion is produced by means of the asymmetric character of the electrode apertures. By using electrode structures of this character, it is not necessary to provide energizing potentials for the particular purpose of producing the fields in the vicinity of the apertures.

The effective potential between the apertured electrode and theysource of the electron beam may'be varied in any desired manner, such as by modifying the potential applied to the apertured electrode while maintaining that of the electron beam source constant or by maintaining the potential of the apertured electrode constant and varying the potential of the electron beam l source. As a further feature of the invention, in cases where the potential impressed upon the apertured electrode is varied, there may also be provided means for correspondingly varying the potential of the luminescent screen in order to maintain a field between these two electrodes l which is substantially constant in intensity.

The .present invention also may include means for providing a plurality of electron beams, each of which has a velocity which is different from the others. In such a case, it is not necessary to provide means for varying the potential of either the apertured electrode or the electron beam source. It is, however, necessary to provide means for switching from one electron beam to another for the production of the different Such a system also necessitates the concurrent Ydeflection of all of the beams and requires Vthat proper registration of the beams be effected in the plane of the luminescent screen.

' The' novel features that are considered characteristic' of this invention are set forth with parti-cularity in the appended claims. The invention itself, however, both as to its organization and 'method of operation, as well as additional Aobjects and'V advantages thereof, will best be understood from the following description taken in connection with the accompanying drawings, in which:

Figure l is a circuit diagram in block form illustrating a color television image reproducing system embodying "the invention;

Figure 2 is an enlarged fragmentary View of an improved form of color-selecting electrode in accordance with the invention and embodied in a cathode ray tube;

Figure 3 is Yanother fragmentary viewV of a typical fluorescent screen electrode forming part of `the 'cathode -ray image reproducing tube;

Figure 4 illustrates another control circuit arrangement for the fluorescent screen anda colorselecting electrode with which the -cathode ray tube may be provided in accordance Ywith the invention; f

Figure 5 is a detailed circuit diagram of one of the circuit components of the television reproducing system shown in Figure 1;

Figure 6 is a series of curves representing voltage waveforms developed at different points of the circuit of Figure 5;

Figure 7 is a detailed circuit diagram of another component of the reproducing system shown in Figure 1;

Figures 8 and 9 illustrate sectional and perspective' views, respectively, of an alternative form of a color-selecting electrode for an image reproducing tube in accordance with this invention;

Figures V10 and 11 illustrate still another form of color-selecting electrode for use in the present system;

Figures 12 and 13 illustrate another alternative form of color-selecting electrode for use in the present system;

Figure 14 is a block, -circuit diagram of another color television image. reproducing system embodying the invention;

Figure 15 is an enlarged fragmentary view of another typical form of color-selecting electrode in accordance with the invention; Y

Figure 16 is a fragmentary view to an enlarged scale of another representative form of fluorescent screen structure with which a cathode ray image reproducing tube in accordance with the invention may be provided;

Figure 1'7 is a series of curves representing typical waveforms of voltages developed and employed in the operation of the color television image reproducing system of Figure 14; and,

Figures 18 and 19 illustrate still another alternative form of color-selecting electrode in accordance with the invention.

Referring first to Figure 1 of the drawings, the color television reproducing system in accordance with the present invention will be generally described. There is provided an antenna I5 which may be coupled to conventional receiving, amplifying and detecting ,circuits I6 by means of which the received carrier wave is ultimately detected so as `to produce thermodulating signal component comprising a composite television signal including Video signals representative of a plurality of color components Vof the image to be reproduced andthe usual system control signals, such as blanking and synchronizing signals. The output of the signal detector circuit is coupled to a video signal separator Ii by means ofl which the video signal component is recovered to the exclusion of the system 'control signals. The video `signal separator is coupled to a video signal amplifier I8, the output circuit of which iscou- Ypled to the electron beam intensity control system ofa -cathode ray image reproducing tube i5. The output of the signal detector circuit i?) alsoV is coupled to a `synclf-irenizing Asignal separator 2i which is coupled to the Adeflecting system of the cathode ray tube I9 in a conventional manner. The synchronizing signal separator 2l aise is coupled to a keying frequency oscillator Ztvvrhich preferably is one capable of developing a sinusoidal voltage at the desired frequency and is susceptible of synchronizing control by mea-ns of impulses Aderived from the synchronizing signal separator 2 I A representative form of the oscil- For example, in a system wherein complete fields of `diierent colors are transmitted sequentially,

the oscillator 23 will develop a sine Wave voltage having the field frequency. In a system in which the color changes are eected in sequential horizontal lines of the image to be reproduced, the oscillator 23 will develop a voltage having the line frequency. In a system which will be treated herein as a preferred form of the invention,`

wherein the color video signals are changed for every dot or elemental area of the image to be reproduced, the oscillator 23 is required to develop a voltage having the dot frequency of the reproduced image. Such `a system is presently referred to as one which operates according to the dot multiplex principle and forms the subject matter of a copending United States application of John Evans, Serial No. 111,384, filed August 20, 1949, and entitled Color Television.

The sinusoidal voltage developed in the output circuit of the keying frequency of the oscillator 23 is represented at 24 and is impressed upon a source of keying voltages 25. The circuit details of this circuit component will be treated more fully hereinafter. Theremay be derived from the keying voltage source 25 two voltages having generally the waveforms shown at 26 and 21. These voltages are impressed upon keying voltage adder 28, the details of which will be more fully disclosed subsequentlyto develop a stepped Wave voltage such as represented at 29.`

This voltage is required to have an amplitudechange frequency corresponding to the colorchange frequency of the received video signals.

The cathode ray image reproducing tube I9 is provided with a conventional electron gun structure including a cathode 3l and electron beam intensity control electrode 32, an electron accelerating electrode 33 and a beam-forming or first anode 34. The output circuit of the video amplifier I8 is coupled to the electrodes 3I` and 32 of the cathode ray tube I9 in a conventional manner, whereby to vary the electron intensity of the beam in accordance with the video signals. The electrodes 33 and 34 have impressed thereon suitable positive potentials in a manner Well known to those skilled in the art. The tube I9 also is provided with a beam-deflecting system which, in this instance, is represented as an electromagnetic yoke 35. The electron beam-deflecting elds produced by the deilectingyoke are varied in a well known manner under the control of saw-tooth voltages derived from the deiiecting control circuits 22 to coupled as shown.

The cathode ray tube I9 also is provided withj an apertured electrode which may be energized` to selectively deflect the beam onto different areas of a luminescent screen capable respectively of emitting light of diierent colors.` In this embodiment of the invention, the electrode 33 comprises a plurality ofspaced plates such as 31 and 38. Only a few of such pairs of plates have been shown in this figure in order to simplify the drawing. It will be understood, however, that there is provided at least as many pairs of plates as there are horizontal lines in the image to be reproduced. Preferably, the

which the yoke is color-selecting i ferred to. that the received video signals successively reprecolor-selecting electrode includes a plurality of pairs of plates for each horizontal image line. These plates may be formed in a manner such as that shown in Figure 2. One set of plates such as 31 may be supported by a vertically extending member 39 and the alternate plates 38 by a vertical member 4|. In this manner, corresponding ones of each pair of plates are connected together electrically so that the supporting members 39 and 4I may be connected externally of the tube to a suitable voltage source such as represented by a battery 42 `in such a manner that the plates 31 are of positive potential with respect to the plates 38. Inasmuch as there is a constant spacing between the plates of all pairs and the same voltage is impressed upon all pairs of plates, there is produced anelectrostatic eld between each pair of plates which is uniform for all pairs. There also is connected to the terminals of the voltage source 42 a potentiometer 43, an intermediate point of which is coupled to the keying voltage adder 2d as shown. By virtue of this circuit arrangement, the potential of the color-selecting electrode 36 may be varied with respect to a reference potential such as ground to which the cathode 3| is connected, While at the same time maintaining a constant field distribution between all pairs of plates 31 and 3B.

The cathode ray tube I9 also is provided with a fluorescent screen 44 which consists of a plurality of groups of areas or horizontal strips such as those represented at 45, 46 and 4l. Each individual fluorescent area of a group is capable of emitting light of a different color. In one embodiment of the invention, the fluorescent screen 44 may take the form shown in Figure 3. Each group of the strips such as 45, 46 and t1 preferably has a sub-elemental width` and a length extending entirely across the face of the cathode ray tube. The elongated areas 4'5, 46 and 41 are formed `of phosphors capable, respectively, of emitting red, blue and green light, for example, when excited by anelectron beam. While, in this embodiment of the invention, it is not absolutely essential to impress a potential upon the screen 44, it may be desirable to do so as indicated in Figure l. In certain other of the illustrative embodiments of the invention disclosed herein, it is necessary that the screen be energized. Accordingly, it is contemplated that the cathode ray tube I9 be provided with a screen having a metallic layer formed thereon which should be suiliciently thin to be electron pervious if placed on the back side of the screen or transparent if placed on the front side of the screen. Such a tube is disclosed in the March 1946, volume VII issue of the RCA Review `at page 5in an article entitled Improved cathode-ray tubes with metal-backed luminescent screens by D. W. Epstein and L. Pensok. In the present instance it may be convenient to electrically connectthe metallic layer to the usual metallic wall coating with which the tube is provided.

Referring now to the general operation of the color television reproducing ,system shown in Figures 1, 2 and 3, it will be assumed that the video signals are bein-gitransmitted and received in accordance with the dot multiplex system re Accordingly, it will be understood sent respectively the component primary colors of each elemental area ofthe image. While the particular orderin which these signalsare received is immaterial, it will be assumed that, in

Vcase previouslyV described.

the present instance, they are received in the order of red, blue and green. Accordingly, when the video signal representing the red component of the first elemental image area, for example, is received and applied to the control electrode 32. of the cathode ray tube I9 to modulate the intensity of the electron beam represented at 48, the keying voltage 29 is at maximum amplitude represented by the step 49. The color-selecting electrode 36, therefore, has impressedV thereon a positive potential of maximum magnitude relative to the cathode 3|. As a consequence, the electron beam 4B has a maximum velocity as it approaches the color-selecting electrode et. The electrostatic eld which is fproduced between Va pair of the color-selecting electrode plates such as 31 and 38 has an intensity such that at this velocity of the electron beam it is deflected by the electrode 35 by a minimum amount as represented at 5|. As a result, it is caused to impinge upon a phosphor strip, such as 45, capable of emitting red light, Y

At the next succeeding instants the received video signal represents the blue color component of the elemental area of the image and the electron beam 48 is modulated in intensity accordingly. At this time, however, the keying voltage 23 has an amplitude such as represented by the step 52 so that the positive potential of the colorselecting electrode 36 is of somewhat smaller magnitude relative to the cathode 3i than in the Consequently, the velocity of the electron beam 48 as it approaches the color-selecting electrode is less than in the preceding instance. eld produced by each pair of the color-selecting electrode plates, such as 31 and 3d, is the seme as the preceding case, theelectron beam is dem ected through a greater angle than previously as indicated at 53. As a result, the beam caused to impinge upon the phosphor strip whereby to emit blue light from the fluorescent screen. K

Similarly, in the next succeeding instant, the received video signal which is impressed upon the intensty control electrode 32 represents the green color component of the elemental image area being considered, whereby the intensity of the electron beam 4B is modulated accordingly. At

this time,'the keying voltage 29 has an amplitude represented by the step 54 so that the velocity ci the electron beam 48 as it approaches the colorn selecting'eleetrode 36 is less than in either of the preceding instances. Consequently, since the electrostatic field between the plates 31 and '33 is unchanged, the beam is deflected through a still greater angle such as represented at 55. ln this oase, the beam is Ycaused to impinge upon the phosphor strip 41, whereby the fluorescent screen 48 emits green light.

This cycle of operation is continued for each of the succeeding elemental areas of the horizontal line of the fluorescent screen 44 being scanned by the beam 4B. It will be understood, of course, that in addition to the color-selecting deiiections given to the electron beam by the color-selecting electrode 36, the beam 4t is den ected over the fluorescent screen 44 in the con-V ventional manner, whereby the screen is scanned in a series of substantially horizontal lines, each from left to right, for example, and successively from top to bottom. During each horizontal dedection of the beam 48 over the vfluorescent screen 4.4, it is caused to pass between at least one pair,

and preferablyV a `plurality iof pairsioi plates,`

Since the Vintensity oi the suchas 3-1 and 38. Accordingly, the vertical de` flection of the beam 48'will cause it to traverse successive pairs of color-selecting deflecting plates. Y

It will be apparent that, while the foregoing detailed description of the operation of a television image reproducing system in accordance with the present invention has been given with reference to the so-called dot multiplex system oi color television, the same cathode ray tube structure may be also employed with substantially equal facility for the reproduction of color television images in either a line sequential system or a field or frame sequential system. The only modication that is required is that relating to the timing of the steps of the keying voltage wave 29. In the dot multiplex color television system, the amplitude of the wave 29 is varied at a rate which is substantially equal to three times the rate at which it is desired to reproduce thethree-color elemental image areas. In a line sequential system of color television, the rate at which the amplitude of the keying voltage wave 2S is varied is equal substantially to the horizontal line frequency. In a eld or frame sequential system of color television, the amplitude of the keying voltage Wave 29 is varied at a rate which is substantially equal to the eld or frame frequency.

It also will be apparent that the present system is susceptible of operation without modication of the described tube structure and with only obvious modifications of the control circuits for eflecting line interlacing of the image to be reproduced according to any desired pattern. Furthermore, it is susceptible of use'in connection with any desired form of dot interlacing such as those shown and described in the copending United States applications of Randall Ballard, Serial No. 117,528, filed September 24, 1949, andrentitled Color Television Systems and Alfred G. Schroeder, Serial No. 117,593, filed September 24, 1949, and entitled Color rFele- Vision.

'In the foregoing description of the embodiment of the invention shown in Figures l, 2 and 3, it was assumed that the positive potential of the fluorescent screen 44 relative to the cathode 3| was maintained substantially constant while the potential of the color-selecting electrode 36 was varied relative to the cathode. As a consequence of this type of operation, it is seen that there also is eifected a Variation in the potential between the fluorescent screen and the color-selecting electrode which, in some cases, may not be entirely desirable. The present invention is of such a character that it is not necessarily limited to such type of operation. An alternative arrangement is illustrated in Figure 4. The plates such as 31 and 38 of the color-selecting electrode 36 are maintained at suitable constant potentials relative to one another by means of a source of voltage such as represented by the battery 42 as in the previously described form of the invention. In this case, a rsuitable positive potential is impressed upon the fluorescent screen 44 by a voltage source suchas represented by the battery 5B, the negative terminal of which, instead of being connected to ground'as in the preceding instance, is connected to the voltage source 42.

Also, in this instance, there is provided a poten` tiometer 51 connected'across both of the voltage sources 42 and 56 and having'an intermediate point thereof connected to the source of keying voltage as inthe previously described embodiment of the invention. Therefore, under the control of the keying voltage, not only is the potential of the color-selecting electrode 36 varied relative to the cathode 3| of the image reproducing tube, but also the potential of the iiuorescent screen is correspondingly varied. As a result, the fluorescent screen and the color-selecting electrode are maintained at a substantially constant potential relative to one another, thereby creating .an electrostatic eld between these two electrodes which is substantially constant in intensity. In many cases, an arrangement of this character will effect a somewhat improved performance of the system.

In order to more completely understand the manner in which the improved color television image reproducing system in accordance with this invention operates, reference will now be made to Figure 5 which illustrates the circuit details of typical apparatus which may be used as the source of keying voltages generally indicated in Figure l. Essentially, it is a type of circuit which is commonly known as a ring multivibrator.

`It comprises as many multivibrators as there are primary color components in the image to be reproduced. In the present three-color television system, there are provided three multivibrators 58, 59 and 6|. inasmuch as these multivibrators are identical, only one will be described in detail.

The multivibrator 58 comprises a pair of vacuum tubes 62 and 63 which, in the present instance, are pentodes. The cathodes and suppressor grids 64 and 65 respectively of the tubes 62 and 63 are connected to ground, as shown. The screen grids 66 and 6'! of the tubes 62 and 63, respectively, are connected together and, through a common voltage dropping resistor 68, to a source of positive voltage indicated at -l-B. The anodes .69 and 1|, respectively, of the tubes 62 and 63 are connected through individual load resistors '|2 and 13 to +B through a common voltage dropping resistor 14 and the |B terminal is bypassed to ground by a capacitor 15.

The anode 69 of the tube 62 is cross-coupled to the control grid 16 of the tube 63 by a network including the parallel connection of a capacitor 11 and a resistor '|8. Similarly, the anode `7| of the tube 63 is cross-coupled to the control grid 19 of the tube B2 by a network including the parallel connection of a capacitor 8| and a resistor 82. Negative biasing voltages are impressed upon the control grids 'I6 and 'I9 of the tubes 63 and 62, respectively, by means of resistors 83 and 84, respectively, connected to a suitable voltage source indicated at -Bias. The control grid 'i6 of the tube 83 is coupled to the terminals of the keying frequency oscillator 23 by means of a circuit which includes a unilaterally conducting device such as a crystal diode 85, shunted to ground by a resistor 86, and a coupling capacitor 81. By means of the polarity in which the diode 85 is connected in the circuit, only the negative half cycles of the sinusoidal voltage wave 24 derived from the keying frequency oscillator 23 are effective upon the control grid 16 of the tube 63. The parameters of the coupling circuit together with the negative biasing potential impressed upon the control grid |6 are of such a character that preferably only the peaks of the negative half cycles are eiective to control the multivibrator 58. The multivibrator 58 may be considered to have an input terminal X connected to the control grid '|6 of the tube 63 and two output ter- 10 minals A and B connected respectively to the anodes 69 and of the tubes 62 and 63.

The multivibrator 59 includes tubes 88 and 89 provided with circuit connections similar to those provided for the tubes of the multivibrator 58. It also is provided with an input terminal Y and two output terminals C and D similar to corresponding terminals of the multivibrator 58. The output terminal B of multivibrator 58 is coupled by a capacitor 9| to the input terminal Y of multivibrator 59.

Multivibrator 6I comprises tubes 92 and 93 and has an input terminal Z and two output terminals E and F. The output terminal D of multivibrator 59 is coupled by a capacitor 94 to the input terminal Z of multivibrator 6|. The output terminal F of multivibrator 6| is coupled by a capacitor to the input terminal X of multivibrator 58.

Voltage impulses having substantially rectangular waveforms may be derived from any of the output terminals of the respective multivibrators 58, 59 and 6|. For the purpose of controlling the operation of the color-selecting electrode such as 36 of Figure 1, the voltages developed at the output terminals C and F of multivibrators 59 and 6|, respectively, are employed.

In order to fully understand the operation of the ring multivibrator illustrated in Figure 5, additional reference will be made to the waveforms shown in Figure 6. A cycle of operation will be assumed to begin at a time when the following conditions exist: tubes 1|, 88 and 92 of multivibrators 58, 59 and 6|., respectively, are in a conducting state and the other tubes are in a non-conducting state. As a result, in addition to the constant negative biasing voltage impressed upon the control grids of the tubes il, 89 and 93, there is a negative potential impressed upon the control grid of the tube 89 of the multivibrator 59 as a result of the conduction of space current in the tube of multivibrator 58. The curves 96, 9'|, 98, 99, IUI and |82 indicate respectively the voltages developed at the output terminals A to F of the multivibrators 58, 59 and 6|. The curve |83 represents the sinusoidal waveform derived from the keying frequency oscillator 23 in its time relation to the voltages developed at the output terminals of the multivibrators.

The peak |94 of the negative half cycle of the wave |83 next occurring following the time assumed for the starting of the cycle impresses a negative voltage on the control grids of the multivibrator tubes 83, 89 and 93. Since the tubes 89 and 93 are non-conducting, this negative driving voltage has no elfect on these tubes. However, the impression of this negative driving voltage impulse upon the control grid of the conducting tube `63 serves to trigger it to a nonconducting state. By reason of the cross-coupling between the anode of the tube 63 and the control grid 19 of the tube 62, this latter tube becomes conducting substantially instantaneously in accordance with well known multivibrator operation. As a result, the voltage at the output terminal B becomes more positive as indicated by the curve 91 and the voltage at the output terminal A becomes less positive as indicated by the curve 96. The impression of the positive voltage impulse developed at the output terminal B upon the inputV terminal Y of the multivibrator 59 causes the previously non-conducting tube 89 to become conducting. By virtue of the cross-coupling between. the anode of the tube 89 and the control grid of the tube cathodes and `theisuppressor grids 11 88, the latter tube becomesnon-conducting. 'As a result, there is developed at the output terminal C of the multivibrator 59 a more positive voltage as indicatedl by the. curve 08 and the voltage developed at the output terminal D is less positive as indicated by the curve 09.

At the occurrence of the next succeeding negative voltage peak |05 of the driving voltage Wave |03, current conduction inthe tube 89 is interrupted and, asa result, current conduction in the tube 8B is again initiated. The positive voltage developed at the output terminal C is decreased, as indicated bythe curve 98 and the Vpositive voltage developed at the output terminal D is increasedas indicated by the curve 90. The impression of the increased positive voltage developed at the output terminal D upon the input terminal Z of. the multivibrator 6| causes the tube 93 to become conducting, which terminates current. conduction in the tube 92. As a n result, the positive V voltage developed at the terminal E of the multivibrator 6| increases as indicated by the curve and the positive voltage developedat the output terminal F decreases as indicatedby the .curve |02.

The next negativevoltage peak |06 of the curve |03 causes the `tube 93 of the multivibrator 6| to become non-conducting, which initiates current conduction in the tube 92, whereby the voltagevdeveloped at theoutput terminal E decreases in positive magnitude as indicated by the curve 10| and the voltage developed at the o utput terminal F' increases as indicated by the curve H52. The increased positive voltage cle-- veloped at the output terminal F. is vimpressed upon the input terminal X of multivibrator 5S to again initiate currentconduction in the tube |53, which results in the termination of current conduction in the tube 62. The described cycle of operation .then is repeated.

For the purpose off developing a control voltage suitable for impression upon the colorselecting electrode 36 of the cathode ray tube I9 of Figurel, the voltages developed at the output `terminals C and El ofthe ring multivibrator, are. employed... These voltages are reprosented by the curves 90 and |02of Figure '1 and are impressed uponthe keying voltage adder 2B of Figure 1.

Having reference now to Figure '1 of the drawings, there are. shown the details of a typical circuit arrangementwhioh may be employed as the keying voltage adder. 28 ofFigure l. it comprises a pair of electron tubes |01 and Vis which, for example, may bey pentodes as shown. rlibe 10u and Hi, respectively, ofthe. tubes |01 and |03 are connected together` and toV ground through a common self-biasing circuitincluding a resistor H2 and a bypass capacitor. I3. The anodes of the tubes` are connected together and through a common load resistonlld to a source of space current indicatedat -i-B. The screen grids H and lr6.. of thetubes. |01=and |08, respectively, are connected together and through a common voltage-dropping resistor ||1-to +B. The control gridllof' the tube |01 is coupled by a capacitor H9 and a leak resistor |2| to the output terminalF of the ring multivibrator of Figure 5. The control grid |22 of the tube |08 is coupled by a capacitor |23 and a leak resistor |24 to the output terminal C of the multivibrator 59 of Figure 5.

Consequently, a voltage having a Waveform such as that shown by the curve |02 of Figure lif) sis impressed upon the control grid Hs of the tube |01 and a voltage having aiwaveform such as that shown by the'curve S8 of Figure Gris impressed upon the control grid |22 of the tube ISB. An inspection of the curve 98 will show that there is developed a series of impulses of positive polarity, `each having a Width or time duration of one unit With a space or time interval of two units between successive impulses. Similarly, an inspection of the curve |02 will show that there is developed at the output terminal D a series of impulses of negative polarity and each having awidth or timeduration of one unit with a space or time interval between successive impulses of. tWo units. A comparison of the time relationship between the positive impulses of the curve 98v and the negative impulses of the curve- |02 shows thatthe respective impulses are not developed concurrently and that there is a time interval of one unit during which there are no impulses developed at the output terminals C and F.

In considering the operation of the keying. voltage adder shown in detail in Figure '7, it Will be understood that during the intervals during- Which no voltage impulses are developedat the multivibrator output terminals C and F as indicated at |25r and |26, respectively, of the curves S38 and |02 of Figure 6, both of the adder tubes |01 and |08 are conducting space current-of -an intermediate magnitude. Under these conditions, the voltage developed at the anodes of these tubes is representedbythe ste-p |21 of the curve |28 which is the waveformof the voltage developed at the output terminal ofthe adder. During the succeeding time interval duringwhich the positive impulse |29 ofthe-curve 98. isimpressed upon the control grid |22 of the tube |08, this tube conducts space `current of armaximum magnitude while the tube |01 continues to conduct space current of the intermediatel magnitude. The resultantrvoltage drop through the load resistor H4 develops a-voltage represented by the step |3| of the curve |28. During the next succeeding interval, the negative impulse |32 of curve |02 is impressed upon the control grid HS of adder-tube Ilwith the result'th-at this tube is caused to conductspacecurrent of a minimum magnitude While the tube |03con ducts space currentof intermediateY magnitude. The resultant voltage drop produced across the load resistor ||l|produces a voltage at'the output of the adder such as represented by the step |33 of curve |28. The describedcycle oi operal tion is then4 repeated. It will be seen Ythat the waveform of the voltage representedl at |23 is that Which is required to vary the potential of the color-selecting electrode 300i Figure 1.

It is to be understood that the embodiment of the present invention which has been described is merely illustrative-offmany alternative embodiments which may be. employed Within the scope of, the invention. Thecolor-selecting electrode 3,6 in the `formgc plates as shown. in Fig-V ures l andu 2 requires an additioI- ral` source of potential for the establishment of thefnecessary electrostatic.iieldsgbetween the dierent pairs of plates. Other embodiments'. of the invention, some` of which are to be described, employ colorselecting electrodes. which do not. require a sep.- arate source of field-producing potential. In order for a color-selecting electrode to function in accordancewith this invention, it is,neces. sary that the electron beam in traversing the apertures of the selecting electrode, be influenced 13 by a iielcl of such a character that it has atleast a component in a transverse direction to that in which the beam is travelling. The plate structure of the color-selecting electrode 36 is of such a character that substantially the entire iield produced thereby is in a transverse directionrelative to the path of the electron beam. As a feature ofthe present invention, there is provided a form of color-selecting electrode which has asymmetric apertures by means of which it is possible to produce a field having a component in a transverse direction to the path of the electron beam.

One such color selecting-electrode |34 is illustrated diagrammatically in Figure 8 of the drawings. This electrode consists essentially of a plurality of bars or wires, such as |35, extending in parallel relationship horizontally in the tube. These bars are spaced apart suitably to define apertures through which the electron beam 48 is directed. The electrode |34 also includes a plurality of smaller bars or wires, such as |36 spaced from the bars |35 on the fluorescent screen side of the aperture-defining bars |35. 'Ihe bars |36 are displaced vertically in an asymmetric manner relative to the apertures deiined by the bars |35 substantially in the manner shown.

Figure 9 illustrates one manner in which the color selecting electrode |34 may be made. The View of this electrode shown in this gure is a perspective as the electrode |34 would be viewed from a point on the electron gun side and looking generally in an upward direction. The aperture deiining bars |35 may be formed by a screen or grid type of structure such that the horizontal bars are supported in spaced relationship by means of a plurality of vertical supporting members, such as |31; Similarly, the asymmetric bars |36 may form part of a similar screen or grid structure in which the bars are supported by a plurality of vertical supporting members such as |38. The supporting members |31 land |38 may be joined together at one or more points by cross members such as |39.

Although not specifically shown in the fragmentary View of Figure `3, it will be understood that there is impressed upon the color-selecting electrode |34 a voltage of positive polarity relative to the cathode of the electron gun, the mag-- nitude of which is varied for color selecting purposes. It will be understood that there is impressed upon the fluorescent screen 44 a higher positive potential. These potentials may be applied and varied in suitable manner. such as illustrated and described with reference to Figures 1 and 4. By reason of the potential difference between the iiuorescent screen 44 and the color-selecting electrode |34, there is produced in the intervening space an electrostatic field. The character of this eld is indicated in Figure 8 by means of representative equipotential lines.

Except in the immediate vicinity of the apertures of the color-selectingelectrode |34, the equi-potential lines are substantially parallel to the plane of the color-selecting electrode. Such an equipotential line is indicated at |4|. As a result of the asymmetric character of the apertures of the electrode |34, the equipotential lines in the immediate vicinity of the apertures are distorted somewhat, as indicated generally by the lines |42. It will be seen, therefore, that within the asymmetric apertures of the colorselecting electrode |34 the lield which exists between it and the fluorescent screen 44 has a component which is transverse to the general direction in which the electron beam is moving through the apertures. This transverse field component is `effective to deflect the electron beam through an angle which depends upon the velocity of the beam. As in the previously described embodiment of the invention, the electron beam velocity is varied by varying the potential of the color-selecting electrode |34 relative to the cathode of the electrode gun. `In this manner, the electron beam is caused to impinge `upon selected areas of the fluorescent screen 44 which are covered by phosphors capable of emitting light of different colors.

Another form of color-selecting electrode is illustrated inFigures 10 and 11. The apertured electrode |43 in this case consists of a plurality ci? horizontal strips, such as |44, having cross `sections which, as indicated, are substantially S-shaped. These may be mounted in spaced relationship so as to form asymmetric apertures substantially as shown by means of a plurality of vertical supporting members, such as the bar |45 in Figure 11. The color-selecting electrode |43 may be energized in substantially the same manner as any of the previously described colorselecting electrodes, whereby to produce a eld which, in the immediate Vicinity of the apertures has a transverse component which is effective to deflect the electron beam 48 substantially as described. i

In Figures 12 and 13 is shown still another form of a color-selecting electrode |46. It comprises a plurality of horizontally extending strips |47 having substantially right angular cross sections. These angularstrips may be mounted within the tube |9 in spaced relationship so as to deline asymmetric apertures by means of a plurality of supporting members, such as |48. The electrode |46 may be energized in the manner described so as to produce a eld component which is transverse to the path of the electron beam, whereby the beam is deected in the manner described for color-selecting purposes.

It is to be understood that the invention is not necessarily limited to embodiments thereof employing a color-selecting electrode having apertures which are of an elongated character arranged so as to be substantially parallel to the direction of horizontal image scansion. Alternatively, the elongated apertures may be disposed substantially at right angles or, in fact, substantially at any angle relative to the direction of horizontal scansion. Assume that in Figure 10, for example, the electron beam 48 is deflected horizontally substantially in the plane of the drawing. The elongated apertures of the colorselecting electrode |43 are disposed substantially perpendicularly to the plane of the drawings and similarly, the sub-elemental phosphor strips of the luminescent screen 44 are arranged at right angles to the plane of the drawing. It will be seen that, as the electron beam 48 is deflected horizontally over successive apertures of the electrocle |43, the velocity thereof is varied as previously described so that the beam is variably deiiected for impingement upon selected ones of Athe sub-elemental phosphor strips. It also will be obvious that substantially any other angular arrangement of the elongated apertures of the `color-selecting electrode may be employed in 'accordance with the invention.

Furthermore,` the invention is not limited to -the use of color-selecting electrodes in whichthe apertures have elongated configurations. As a `matterof fact,it may be preferable to employ a.

@olor-selecting electrodeV inwhicrii-the apertures are discrete openings of substantially any coniig-urationsuoli` ascircular or rectangular apertures; Inaddition', Vthe sub-elemental are-as of the luminescent screenmay be minute discrete circular or rectangular'areas;

Moreover, in accordance Withl another feature of this invention, itisnot essential that the potential difference between thev color-selecting electrode and the electron beam source be varied by means of an abruptly stepped wave voltage. it may be varied sinusoidally, for example. In order to more clearly illustrate: these additional features of the invention, reference now will be made to Figure 14 ofthe drawings.

The color television image reproducing system illustrated ini Figure 145 is in general similar to that shown in Figure land, therefore, particular emphasis will be giv-enonly to the differences in the twosystems. A system of this character is particularly'useful for dot multiplexoperation as disclosed inthe copending U. S. application of John Evans referred' to; where each elemental area ofthe image to be reproduced is represented by successive groups of a plurality ottime-spaced video signals.- While'video signals of' this character may be employed forimage reproducing purposeswith any ofthe previously described embodiments of the invention by impressing the received video signals directly upon the intensity control electrode ofthe cathode ray imagev reproducing tube, it isnecessary in the present embodiment of the invention to suitably time the impression of the respective video signals upon the electron beam intensity control: electrode.

ForV this ipurpose, the :receiving system employs a gatingdevice- |l coupledV inthe video signal channel. The details of thegatingdevice have 'not been specifically shown for the reason that it may beentirelyconventional consisting, for eX- ample, of 'one ormore electron' tubes' having an input circuit coupled tothe video signalsepar'ator andan outputE circuit coupled to the video amplifier Itu and normally biased'beyondl cutoff so "that-video signals-are not impress'eduponthe intensity control electrode 32vv of the cathode ray tube i9'.Y At predetermined intervals the biasing ofthe gatingdevice is suitably altered toi render it conducting, whereby the video signal' impressed at that time upon the input circuit is also impressed upon the intensity control' electrode 32. Another gating: device Which=maybe used is-similar to that disclosed in SL Patent No. 2,563,406, granted August 7, 19517, to E. A. Goldberg andY titled Electronic Commutator. The Goldberg system employs aiunilaterally conducting device such as a crystal diode, or a bridge arrangement of. a number of such diodes, coupled in series in the signal conveyingcircuit and suitably biased'to periodically render 'the device conductive.

The system also includes a keying voltage oscillator Y23 suchas that previously described in connection with'the systemofFigure 1 and which is capable off producing an output voltage having a substantially sine wave form such as represented at |52V andal frequency equalto the elemental scanning-*'frequencyg that is-', the frequency at which thez multiplicity off elemental image areas are. scanned The outputcircuitoflthe keying voltage oscillatorliisffcoupled.to arfr'equency multiplier which', inthe-case ofl athree'eolorv system; is afrequencytripler' |53;V Thevoltage produced in the:l output circuit' of. the frequency :multiplierA iszf'impressedr upon the control circuit "of' the gatingv device |25|i by means of` a phase adjuster |54` and. also is sinusoidal as represented atA |555,

Also, in accordance with this embodiment of the invention, the cathode ray tube I9 is providedwith a foraminous color-selecting electrode |356- having a plurality of` substantially circular -apertu-reswliich are in effect asymmetric in order to provide the desired distortion of the electrostatic''eld` existing between the electrode |56 and a luminescent screen |51, whereby to effect deflectionV ofv the electron beam' for' color selecting purposes.

A facel view ofthe colorlselectingelectrode |56 is showin to an enlarged scale in Figure 15; The apertures such as |58' are substantially circular and theelectrodel is formedl with protuberances such asA |59.v immediately above each of the apertures so as to effect the desired distortion of the 'electrostatic flldl 'The luminescent: screen |51 may, if desired, be :formed in substantially the same manner as that previously. described wherein phosphors capable respectively of. emitting light of different colors are arranged. inparallel strips either horizontally, vertically or at any other intermediate angles. Alternatively, the'luminescent screen 51 may be Vformed substantially in the manner shown in Figure 16. The different color-emitting phosphors arel arranged in this form of screen in discrete areaswhich, for example, may be circular as. shown. Ar group of discrete phosphor areas is associated with each of theapertures of the colorselectingelectrode |56.. For example, the aperture |58 oiY the-electrode |56 may have associated therewith 'the-phosphor areas |6|, |62 and --li capable respectively of emitting red, blue and green. iight when. excited by an electron beam.

The color' television image reproducing system of Figure 14 operates substantially in the following manner: the potential of the color-selecting electrode |56 is varied relativev to the grounded cathode 3|- by means of the voltage wave |52 substantially in accordance with a sine function', whereby to correspondingly vary the rvelocity of the electron beam 48. Theelectron beam, however, is not-continuous but, in accordance with this-embodiment 'of the-invention, is

.keyed at the frequency at which the video signais are changed from one image color to another.

In orderV to better understand.theroperation of this-embodiment of the invention, additional Vreference will. be made to` Figure 17. The curve |52.Y representsl the voltage impressed upon the .color-selecting-electrode 56.V The curvefl 55 rep- -r-esents` the control voltage Vimpressed upon the gating device |51. The* phase adjuster |555' is eiiective to-actuate the gating device |5| at preselected timesV corresponding-to diiierent ampli- ,tudesrot the voltage Wave |52. Assumerthat the gating deviceu isrenderedv operative under the controiofthe` positive; peaks of the control Voltage wave |-55. If, by meanszofr the phase adjuster, the positive. peak |84 is adjusted to occur Aatthetime:vvhenthe.amplitude of the wave |52 isas represented-at and this time coincides with the time ofreception of the-red video-signal, it-isseen that the electronbeam 48 is modulated- .ini .intensity Vinaccordance with. the red .video signal and, sincethe color-selectingelectrode |561. has. impressed thereon a positive potentialiof appreciabiemagnitude relative to the cathode3|,1thebeam-velocityl is high. Therefore, irl-traversing. the field produced in the vlapertured electrode may be tapada@ fcinityof one cffthe-aperturesfofsthe color-'select- `'ing electrode r|f56,1the beamais deflectedto a miniimum= degree and4 is caused to excite a redphoslphorfscreenV area. In a three color system, the

peak |64 of thewwave'fl may be made to oc- Similarly the next Apositive peak |68'of the rWave-|55 occurs coincidentally with the-reception of` a green video signaland'at a time reprefsentedfbythe point |69 of the `wave |52. `As a \result,. a` minimum `voltageis impressed upon the .color-selecting electrode |567 whereby tocause the-l'deection-'of the 'electron `beam for impingement uponva greendphosphor area. The de- `scribed-cycle of operation is thenrepeated for the 'nextisuccee'ding elemental area of the image to `-bereprodu'ced l It will be seen that, even though thevwave |52 impresses a voltage of any given lmagnitude upon thecolor-selecting electrode |56 `twiceduring` a cycleythe electrode is rendered `incapableloriexciting the 'same color phosphor area twicecluring a cycleof operation by prop- `e'rly 'phasing the"relationship between the waves |f52 and |55 'substantially' 'in Athe manner described. l

:Figures 18 andl19 illustra'testillanother form of color-selecting electrode inlaccordance with Athis' invention. In this embodimenttheelectrode consistsof two foraminous members o r` perforated plates A|f|| and |12 arrangedfin spaced parallel relationship substantially asrshown in Figure 19. The plate |12. which is of 4the' electrodeis provided with alpluralitylof smallapertures such as |`|3,f`whereasthe plate l `which is-` adjacentfto l the luminescent screen isprovidedfwith a corresponding number of aper- "tures "Hd but of somewhat larger size. 'Eachpair -of Y apertures f is a'rranged eccentrically` substan- "tiallyfas shown sofas toefectthe described dis- #tortion of 'the electrostatic `neld produced' beon the electron gun 'iside` -l electron beam 48: as` it impinges `upon `the colorl l selecting electrode.

" tween the color-selecting electrode` and the lumiynescent screen.

-'I'heapertureslneed not be circular'as shown ibut,=as" will be-'unclerstood by those skilled in the -artfmaylhave other configurations such as rectangular or-square ones, for example. `The apertures may be aligned both vertically `and hori.

v"zontally orthey may bei-staggered substantially as yshown infFigure 118. The arrangement `ofthe apertures `need not necessarilybe according to iafregular pattern but alternatively may be entirely random in character. In such a case/the employed in the formation of the luminescent screen. It is only necessary that fthe sub-elemental screen 1 areas be made to correspond with color-selecting electrode apertures.

`In""0rcler to `simplify the Edescrmtion'of the apparatus and its mode of operationin conjunc- "tion-with anyfof 'the embodiments Yofltheinven- `ltion shown and described, reference has been made to' the A electron beam and -the -manner in4 i poses-byfa single screen aperture. understood that it Vis notan essential Vrequiretures.

time, a plurality ent portions of the `electron beam. `A representa- 1ferentso that they would -iby the coloreselecting electrode. `Inusuch a case,

herein. It would7 however,` fthe respective beams *on* and 'off in synchronism `with'ithe 'reception of video foffdifferent colorcomponents of thefimage to be 18 which it is controlled for color-selecting pur- `It is to be ment of the present inventionlthatl-the electron .beam Y"befmade to 'register throughout: a given horizontal deflection thereof withonly one hori- .zontally arranged elongated-aperture or withA a horizontal row of a plurality vofdiscrete aper- Actually, it is preferable that the number of screen apertures tbe` suiiicient that, at anyone ofi-them is traversed by differtion of such` an arrangement is givenfin Figures 18 and `19. The broken line circle-of Figure 18 represents a typical cross-sectional area of the Only `those portionsr of the electron `beam which `are in register withthe fdening apertures of the color-selecting electrode are effective to excitetheH-luminescent screen. It

fecting the colorselection operation'in `accordance with the invention.

While the present y'invention has been shown and rdescribed particularlywith reference to a rsingleelectron ybearxnthe deflectionoflwhich for color selecting purposesis effected-by an apertured color-selecting electrode, it willbe `obvious to those'skilled in the 'art that the principles-of the present invention are equally applicable 1to `the control of aplurality ofielectron beams. l The velocities of `therespective-beams would be difbe differently deiiected however, the Vpotentials impressed `between Athe `colon-selecting,r electrode and the-cathodes, `for example, `of the respective electron beams while diierent for each ofthe beams would be fixed.

It'iwould, thereforegnot lbe necessary to provide a varying amplitude-voltage' wave for thecontrol ofthe electron beam velocities as inthe particullar embodiments rof `:the invention described be necessary to key `signals representative reproduced. 'A representative exampleof amul- `tiple electrongun arrangement for. use in an -image reproducingtubein a color television systemis shown in U. S. Patent No. 2,481,839,

`granted September 13, 1949; tolA. N. Goldsmith Ifor Color Television.

Also, it will be obviousto those skilled in the `artthat "the velocity of theelectron scanning beam may be varied for"colorselecting purposes "in accordance with this invention byV varying the potential of the cathode, `electron `gun relative to a colorselecting electrode. Other equally obvious -means may be employed for varying the velocity `for example, of the xedpotential of the of'the electron scanning beam so that it may be variablydeilected for color-selecting purposes by an l apertured electrode such` as any of those 'shown and described `herein-or their equivalents.

Itawill beunderstood that the invention is not limited tothe embodiments'thereof which have `been `disclosed herein for thepurpose of `illustrating the underlying principles of the inven` tion, `the-scope ofA which may; be determinedfrom the= following claims.

u scan said screen responding to the color-change frequency 'video signals, means associated with said tube Yto loe-reproduced change frequency of said I claim:

Y,Il /Acolor ode ray imageV reproducing tube including a source of an electron beam and a fiuorescent screen having a plurality of groups of areas re- Vtensity of said beam, means for deflecting said "beam according to a predetermined pattern to in complete image fields, a source of keying voltage having a frequency corof said for developing a beam-deflecting field for additionally deflecting said beam in an amount dependent upon the velocity of said beam, and means responsive toV said keying voltage to vary the velocity of said beam concurrently with-color changes of said video signals, whereby to selectelevisionrsystem, compris'ingra cath-.

to 'said keying voltage for varying the potential vbetweensaid field developing electrode and said electron beam source to vary the velocity of said beam concurrently with color changes of said video signals, wherebyV to selectively excite the differently colored light emitting areas of said screen in coincidence with the intensitymodulation of said beam in accordance with the different image color components. l

4. A color televisionV system, comprising a cathode ray image reproducing tube including a source of an electron beam and a fluorescent screen having a plurality of groups of areas respectively capable of emitting light of different colors when excited by said beam, means responsive to received vdeo'signals representative of differently colored light components of the image to be reproduced for modulating the intensityY of said beam, means for deflecting said'beam accordingto a'predetermined pattern to scansaid screen in complete image eldsymeans responsive to received synchronizing signals for gentively excite the differently colored light emitting areas of said screen in coincidence with the intensity modulation of said beam in accordance with the different image color components.

2. A color television system, comprising a cathode ray image reproducing tube including a source of an electron beam and a fiuorescent screen having a plurality of groups'of areas respectively capable of emitting light of different colors when excited by said beam, means responsive to received video signals representative of differently colored light components of the image to be reproduced for modulating the intensity of said beam, means for deflecting said beam according to a'predetermined pattern to scan said screen in complete image fields, means for generating a keying voltage having a magnitude varying at a frequency corresponding to the color-change frequency of said vide-o signals, means including an electrode mounted in said tube for developing a beam-deflecting field for additionally deflecting said beam in an amount dependent upon the velocity of said beam, and means responsive to said keying voltage for varying the potential of said field-developing electrode to vary the velocity of said beam concurrently with color changes of said video signals, Whereby to selectively excite the differently colored light emitting areas of said screen in coincidence with the'intensity modulation of said beam in accordance with the different image color components. Y

3. A color television system, comprising a cathode ray image reproducing tube including a source of an electron beam and a fluorescent screen having a plurality of groups of areas respectively capable of emitting light of different colors' when excited by said-beam, means responsive toV received video signals representative of differently colored light components of the image for modulating the intensity of said beam, means for deflecting said beam according to a predetermined pattern to scan said screen incomplete image fields, means for gen- .erating a fvarying amplitude keying voltage havingV a frequency corresponding to the colorvideo signals, means including an electrode located adjacent to the path of said beam for developing a beam-deflecting field of substantially uniform intensity in all Vlelemental portions thereof for additionally defleeting said beamrin an amount dependent upon thevelocity of said beam, and means responsive erating a' stepped Wave keying voltage having anV amplitude-change frequency corresponding to the color-change frequency of said video signals, means including an apertured electrode located in the path of said beam for developing a'beamdeflecting field of substantially uniform intensity in all elemental portions thereof for additional-Y l ly deflecting said beam in an amount dependent upon the velocity of said beam, and means for impressing said keying voltage between said field developing electrode and said electron beam source to vary the velocity of said beam con'-V currently with color changes of said video signals, whereby to selectively excite the differently colored'light emitting areas of said screenV in coincidence With the intensity modulation of said beam in accordance with the different image color components. Y Y

5. AV color television system, comprising a cathode ray image reproducing tube 'including a source of an electron beam and a fluorescent screen having a plurality of groups of areas respectively capable of emitting light of different colors when excited by said beam, means responsive toreceived video signals representative of 'Y differently colored light components of the image to be reproduced for modulating the intensity of said beam, means for deflecting said bea-m according to a predetermined pattern to scan said screen in complete image elds, means for generating a steppedwave keying voltage having an amplitude-change frequency corresponding to the color-change frequency of said video signals, means including an electrode located in the path of said beamfor developing'a beam-defiecting field of substantially uniform intensity in all Y yelemental'portions thereof for additionally defleetingY said beam in an amount dependent upon the velocity of said beam, and means for impressing said keying voltage upon VSaid field-de-v veloping electrode to vary theV velocity Yof said beam' concurrently with color changes of said video signals, whereby to selectively excite the differently colored light Vemitting areas of said screen in coincidence with the intensity modulation of said beam in accordance with the different image color components.

6. A' color television system, comprising a cathode ray image reproducing tube including a source of an electron beam and a fluorescent Yscreen having a plurality of groups of areas respectively capable of emitting light ofdifferent colors when impinged by sa1d beam, means for `said electrode `group of said areas having `zont'al imageline Width," means "for modulating modulating-the intensityfofa said beam fine-faccordance with video signalsxrepresentative `of diierently colored light components ot theimage to be reproduced, means for 4scanningsaid screen by saidbeam in a predetermined patterng'means including an apertured electrode amounted in `spaced relation to 'said "screen-fand to said beam source for producing a plurality of"e1ds tobe traversed by said beam, and means including for varying the `velocity of fs'aid beam in its Atraversal of said `fields to'feifect Aselective impingement `of said, beam lupon the "difierently colored light emitting areas offsaid screen-in coincidence with the intensity modulation of said beam inaccordance'with the dierent image color components.

7. A color television system, comprising a cathode ray image reproducing tube `including a `source of an electron` beam and afluorescent screen having a plurality of groups of` areasrespectively capable of emittinglight of different colors when impinged by said beam, means for modulating the intensity of said beam in accordance With video signals representativeof differently colored light components of the'vimage to be reproduced, means for scanning said screen by said beam in alpredetermined pattern, means including an electrode having an elongated aperture for each of said groups of screen areas andmounted inspaced'relation tofsaid` `.screen and to said beam source for producing a plurality of electron deflecting fields to be trav- `ersed bysaid beam, and means including said electrode for varying thevelocity of said `beam in its traversal of said elds toleiect' selective gA impingement of said beam upon the diierently colored light emitting areas of `said screen Vin coincidence with theintensity modulation of said beam in accordance with the different image color components.

8. A color television system; comprising a `cathode ray image reproducing tubedncludingha source of an electron `beam anda lfluorescent "screen havinga-plurality of groups of-elongated substantially horizontal ``areas respectively capable of` emitting lightV of `different `-colors l when impinged by said'beam, saidscreen areasbeing of sub-elemental Width, -means for modulating the intensity of said beam in accordance with video signals representative: of `diierentlyl colored lightcomponents of thelimalgeftobe reproduced,

ymeans for-scanning said screen by-#said `bearrr-"in Va predeterminedpattern, means including ahori- -aontally apertured electrodemounted infspaced screen f and to said beam source relationto said for producing aplurality of "transverseiiields Ito be traversed by said beampand means-*including said electrodefor varying the 1velocityjof saidbeam inrits traversal of `saidilelds1to effect selective impingement off `said beam `upon Athe differently colored `light emitting areas-of said `screenin coincidence withlthe intensitymodulation of said beam "in accordance with fthe different imagecolor components. l

9. A color television systemfcomprisinga cathode ray image reproducing tubeincluding y-a source of i an electron beamand a lfiuorescent Yscreen having a pluralityiof groups of elongated substantially "f horizontal andaparal-lel tareas frespectively capable of emitting light of different colors when impinged by `said beam, said? screen Width `and `each Tan elemental horiareas being fof "subaelemental the intensity `of s'aidvbeam A'ini accordance With `said beam; and means l0 `said screen, said selective Vupon `the energization of saidcolor-selecting apored vlight'fcomponents fof the image to Abe reproduced, Ameans for scanning said. screen `:by 4said beam in a predetermined pattern, means including an electrode'having an elongated: substantially horizontal aperture `for eachl ofl said-"groups offscreen` areas andmounted between saidscreen vand said beam source for `producing aplurality of transverseV electric fields tobe traversed by `including `said electrode for varying the velocity ofsaid beam in its traversal of said fields toV eiect selective impingement of said beam upon the diierently colored light emittingareas of said screen in coincidence with the intensity modulation of said bearnin accordance with the different Aimage color` com- `ponents.

l0. A `color `television image reproducingsystem wherein diierent video signals represent different color components of the image to be reproduced, comprising a'lcathode ray image repro- Vducing tube including a source of electronspa luminescent screen capable of emitting light of different colors when excited by and color-selecting means associated with said cathode ray tube to control said electrons for `selective excitation of said screen, said selective excitation depending upon Ythe magnitude ofthe energization of said color-selecting meansJneans for sinusoidally varying the energization of said color-selecting means, and 'means to supplyelectrons from said source `varying inintensity in accordance with received video signals and at a `rate harmonically :related to said sinusoidal variation of'said color-selecting means energiza-` tion.

11. A color television image `reproducing system wherein each elemental area of the image to be reproduced is `represented by successive groups of a plurality of time-spaced video signals, comprising a cathode rayimage` reproducing tube including means energizable to produce an electron beam, a luminescent screen capable of emitting light of diiTerent colors when selectively excited by said beam, and color-selecting apparatus associated With said cathode ray tube `to control `saidbeam for selective excitation of excitation depending paratus, means for sinusoidally varying the energization of said color-selecting apparatus, and means for periodically energizing said electron beam producing means in accordance with received video signals at a harmonic of the' frequency of saidsinusoidal energizationof said color-selecting apparatus.

l2. 'A colorltelevision image reproducingsystem wherein each elemental area ofthe image lto be reproduced is represented by `successive groupsfof a plurality of time-spaced video signals, `co'.npr1'sing a cathode ray image reproducing tube including a `sourceof` an electron beam, a luminescent screen having aplurality of groups of areas respectively capable of emitting light of diierent colors when excited by said beam, and a colorselecting electrode to controlsaid beam for selec-` depending upon the Venergization of `said electrode, means for `sinusoidally varying the energia--` ing potential of said electrode, and for intermittently modulatingsaid in accordance `with received video signals ata rate equal'to a `nfiultiple of saidsinusoidal potential variation.

13. A coloritelevision system wherein different video signals represen different color components "of the image f-tobe nreproduced;comprissaid electrons,

Y different colors when selectively impinged by Y apparatus energy.

ing a cathode ray image reproducing tube having a luminescent screen capable of emitting light of e. ectrons, color-selecting apparatus for controlling electrons for selective impingement of said screen associated with said cathode ray tube in accordance with the energization of said apparatus, means for developing energy of a variable magnitude having a sinusoidal wave form and a frequency'related to the color-change frequency of received video signals and applying said energy to said color-selecting apparatus, means for developing energy having a frequency harmonically related to the frequency of said color-selecting monic energy and received video signals to develop and direct groups of electrons toward said screen at said harmonic frequency, and means to adjust the relative phase ofsaid sinusoidal en- -ergy and said harmonic energy suitably to effect the development of said groups of electrons at different magnitudes of said sinusoidal energy.

14. A color television image reproducing system Vwherein each elemental area of the image to be reproduced is represented by successive groups of a'plurality of time-spaced video signals, comprising a cathode ray image reproducing tube including a source of an electron beam, a luminescent screen having a plurality of groups of areas respectively capable of emitting light of different colors when excited by said beam, and an electron-pervious color-selecting electrode interposed between said screen and said electron source to effect color-selecting deflection of portions of said beam to respective ones of said screen areas capable of emitting light of a selected color depending upon the energization of said electrode, means for sinusoidally varying the energizing potential Yof said electrode, and means for modulating said beam in accordance with received videoV signals at a rate equal to a multiple of said sinusoidal potential variation.

15. A color television image reproducing system wherein each elemental area of the image to be reproduced is represented by successive groups of a plurality of time-spaced video signals, comprising a cathode ray image reproducing tube including a source of an electron beam, a luminescent screen having a plurality of groups of areas respectively capable of emitting light of Vdifferent c colors when excited by said beam, and an apertured color-selecting electrode interposed between said screen and said electron source, said Aapertures serving to effect color-selecting deliection of portions of said beam to respective ones of said screen areas capable of emitting light of a selected color depending upon the energization of said electrode, means for sinusoidally varying the energizing potential of said electrode at the i image elemental scanning rate, and meansA for modulating said beam in accordance with received video signals at a rate equal to a multiple of said elemental scanning rate.

` 16. A color television image reproducing system wherein each elemental area of the imagev to be reproduced isv represented by successive groupsof a plurality of time-spaced video signals, comprising a cathode ray imageV reproducingY tube-including a source of an electron beam, a luminescent Yscreen having a pluralityof groups of areasrespectivelyY capable of emittingY light of Vdifferent Vcolors lwhen excited by said beam, and an apermeans controlled by said har- Y tured electrode interposed between said screen ,and saidV electronV source, said apertures being positioned to eiect registration of portions of said beam and corresponding groups of said Y color-selecting deection of said registered beam portions to respective ones of said screen areas capable of emitting lightof a selected color depending upon the energization of said electrode, means for sinusoidally varying the energizing potential of said electrode at the image elemental scanning rate, and means for modulating said beam in accordance with received video signals at a rate equal to a multiple of said elemental scanning rate corresponding to the'number of component colors in which the image is to be reproduced.

1'7. A color television image reproducing system wherein each elemental area of the image to be reproduced is represented by successive groups of a plurality of time-spaced video signals, comprising a cathode ray image reproducing tube including a sourceof an electron beam, a luminescent screen having a plurality of groups of areas respectively capable of emitting light of different colors when excited by said beam, and an apertured electrode interposed between said screen and said electron source, said apertures being Vpositioned to effect registration of portions of said beam Y and corresponding groupsV of said screen areas and also being asymmetric to effect color-selecting deection of said registered beam portionslto respective ones of said screen areas capable of emitting light of a selected color depending upon the energization of said electrode, means for sinusoidally varying the energizing potential of said electrode relative to the potential of said electron beam source at the image elemental scanning rate, and means for intermittently modulating said beam in accordance with received video signals at a rate equal to a multiple of Vsaid elemental scanning rate corresponding to the number of component colors in image is to be reproduced. Y

18. A color television image reproducing system wherein each elemental area of the image to be reproduced is representedY by successive which the groups of a plurality of time-spacedrvi'deo sigregisteredbeam portions to` respective ones of Y said screenV areas capable ofV emitting light ofa selected color depending upon the energization of said electrode, means for sinusoidally varying Y the energizing potential of said electrode'at the Y image elemental scanning rate, means for intermittently modulating said beam in accordance with received video signals at a rate equal toga multiple of said elemental scanning rate corresponding to the number of Vcomponent colors in which the image is to be reproduced, and means for timing said intermittent beam modulation for occurrence substantiallyV at 60, andY 300 degree points of said sinusoidal potential varia- A tion. Y

19. In a cathode ray tube for use in a color television system, a luminescentV screen having v Ya plurality of groups of discrete adjacent areas 'of sub-elemental dimensions, said areas being` capable'respectively 0f emitting differently col-V VVcred light when impingedrby an electron beam.

and, as color-selecting electrodei` located rinthe, pathof an; electron;` beamy directedytowardrsaid screen, saidelectrode` having, for` each of :said groups ofscreen1areas,\. a discrete.asynfimetric.` aperture in the `vicinityofg.` each of` Which-to 'prce duce a iield for delecting an electroncbeamffor: impingement upon selected :onesfoiusaid subelemental areas 20.In a, cathode ray,` tube forense-in: a colori television` system, a; luminescent screen:` having a plurality of` groups; ofadjacentwareascfz ISub-. elemental dimensions, said areasa` being, capable respectively of emitting diiierently:colorediA lightu when impinged by ani,electrongbeamfanda color.n selecting electrodeV located in y ther-pathi off an electron beam directed r toward; saidvscreen, said:

electrode comprising two grid structuresmounted;V

in parallel planes:substantially.` normalntc:the` path of the electronlbeam, eachofisaidgii .i structures including; a plurality of spaced substantially parallel members defining elongated apertures in said respective structures, and the members of one of saidgstructures being displaced relative to the corresponding members of` the other of said structures, thereby definingesyme metric `apertures in the vicinityY of Whichltdproduce fields for deiiecting an electron beamm for impingement upon selected ones `of saidsubelemental .screen areas.

21. In a cathode ray tube for use in a color television system, a luminescent screen. having a plurality of groups of, adjacent areasconsub.- elemental dimensions,` saidareascbeing capable respectively of emitting diierently' colored light when impingedby an electron beam, and a color selectingelectrode located` in `the path of an electron beam f directed towardr said screen, said electrode comprising a plurality of space-d substantially parallel members of S-shaped crosssectional conguration defining elongated asymmetric apertures in the Vicinity of which to produce fields for deiiecting an electron beam for impingement upon selected ones of said subelemental screen areas.

22. In a cathode ray tube for use in a color television system, a luminescent screen having a plurality of groups of adjacent areas of subelemental dimensions, said areas being capable respectively of emitting diierently colored light when impinged by an electron beam, and a colorselecting electrode located in the path of an r electron beam directed toward said screen, said electrode comprising a plurality of spaced substantially parallel members of right-angular cross-sectional conguration dening elongated asymmetric apertures in the vicinity of which to produce elds for deecting an electrode beam for impingement upon selected ones of said subelemental screen areas.

23. In a cathode ray tube for use in a color television system, a luminescent screen .having a plurality of groups of adjacent areas of subelemental dimensions, said areas being capable respectively of emitting dilerently colored light when impinged by an electron beam, and a colorselecting electrode located in the path of an electron beam directed toward said screen, said electrode comprising a foraminous structure having protuberances formed on one face thereof adjacent corresponding portions of the apertures of said structure, thereby providing asymmetric apertures in the vicinity of which to produce fields for deiiecting an electron beam for impingement upon selected ones of said sub-elemental screen areas.

24. In a cathode ray tube for use in a color vious,` color-selecting` television system; a` luminescent screen., having. a plurality `of: groups` `of: adjacent areasnofA sube` elemental dimensions, 4.said areas,` being; jcapable, respectively ofemitting differently oeloredlight.` when impinged by an :electron `beam; and a Acolorselecting electrode located inthe pathof an lelece' tron-beam directed toward saidscreen; saidfelec-e trede comprising` two` foraminous:l structures,` mountedfin parallel planes substantially normal tonthe ,path of, fan electron; beam,` thee apertures;` or.` oneuof` said structures being larger than-i and displacedrelative Ato the. apertures of` the other of said structures,` i thereby ,'dening y asymmetric4 apertures` in theA vicinity` of;` which `to produce:` fields, for derlecting an: electron beam for imi, pingement upon selected ones ofwsaidwsubrele-:f mental screen areas.

25. Inza, color `television systemya cathodelzray,` image reproducing` `tube including a scurcetofant electron beam; aluminescent screen spacedafromi said beam source andchaving a plurality.;` of groups :or areas .respectively` v'capable cfa emitting light of different colors when excitedzby yantelecp-` tron beam, meansmincluding an` electronfpere` electrode mounted spaced `relation to Ysaid i. screen f andrto said: beam' source and variablyenergizable,to selectively; deiiect said beam to` `respective ones ofsaid:y differently colored light-,emitting screen areas,

and means accelerating :said ,selectively adeiectedl beam in the region between.` saidlcolor-selecting electrodevand said screen.

26. In a color televisionsystem, a cathcdexray.;` image reproducingtube `including a 'source ofi; a

` relatively 4low velocity electron beam, a luminese` cent'1 i screen spacedl fromc said f beam'` source rand@ having a plurality of groups ofsareasrrespectivelyf capable of emitting light of different colors when excited by an electron beam, means including an electron-pervious color-selecting electrode mounted in spaced relation to said screen and to said beam source to effect color-selecting defiection of said beam to respective ones of said differently colored light-emitting screen areas depending upon the energization of said electrode, means for varying the energization of said electrode at the image color-changing rate, and means producing a iield between said screen and said color-selecting electrode to increase the velocity of said beam after said color-selecting deflection thereof.

27. In a color television system, a cathode ray image reproducing tube including a source of an electron beam, a luminescent screen spaced from said beam source and having a plurality of groups of areas respectively capable of emitting light of diierent colors when excited by said beam, and color-selecting means including an electron-pervious electrode mounted between light-emitting areas of said screen, the magnitude of said color-selecting beam deflection being dependent upon the relationship of said iields and the velocity of said beam, means in.. cluding said electrode to vary said relationship periodically, and

acter tending to accelerate said beam.

28. In a color television system, a cathode ray image reproducing tube including a source of an electron beam, a luminescent screen spaced from s'aid beam source and having a plurality of groups of mutually parallel phosphor strips respectively capable of emitting light of diierent colors when excited by said beam, means including anV apertured color-selecting electrode mounted between said screen and said beam source in the vicinity of said screen and energizable to selectively deect said beam to respective ones of said differently colored lightemitting strips, said color-selecting electrode having means dening elongated apertures for andY in substantial alignment with respective groups of said phosphor strips, means energizing said color-selecting electrode in a manner to produce beam-'deilecting fields in said apertures, means varying said color-selecting electrode energization to eiect said selective beam defleetion, and means impressing upon said screen a potential of positive polarity relative to the potential of said color-selecting electrode. Y

29. In a color television system, apparatus as Y defined in claim 28 wherein, said color-selecting electrode aperture-dening means comprises, a plurality of substantially parallel elongated metallic members, alternate ones of said metallic members being connected together electrically to form two interleaved meshes, and said colorselecting electrode energizing means includes a source of potential coupled to said respective meshes in opposite polarities.

30. In a cathode ray tube for use in a color television system, a luminescent screen having a plurality of groups of adjacent areas of sub elemental dimensions, said areas being capable respectively of emitting differently colored light when excited by an electron beam, and a colorselecting electrode located in the path of an 28 electron beam directed toward said screen, said electrode having a plurality of asymmetric apertures in the vicinity of each of which to produce a eld for deflecting an electron beam'for impingement upon selected' ones of said sub-elemental screen areas. Y

31. A cathode ray tube as defined in claim 30,1 in which said screen areas are elongated and Y are of sub-elemental width, and said electrode apertures are defined by members extending'in the direction of said elongated screen areas 32. A cathode ray tube as dened in claim 30, in which said screen areas are elongated and are of sub-elemental width, and said color-selecting electrode has a cross-sectional coniivguration in a direction substantially at right angles to said elongated screen areaslto define said asymmetric apertures extending in the direction of said elongated screen areas. Y v

Y PAUL K. WEIMERZv References Cited in the ile of this patent UNITED STATES PATENTS 

